Process of preparing lubricant additives



United States Patent O 3,216,936 PROCESS OF PREPARING LUBRICANTADDITIVES William M. Le Suer, Cleveland, Ohio, assignor to The LubrizolCorporation, Wicklitfe, Ohio, a corporation of Ohio No Drawing. FiledMar. 2, 1964, Ser. No. 348,820 20 Claims. (Cl. 252-321) This applicationis a continuation-in-part of copending application Ser. No. 62,092,filed October 12, 1960, now abandoned.

This invention relates to oil-soluble, nitrogen-containing compositionsand in a more particular sense it relates to such compositions derivedfrom acylation of alkylene amines. The compositions of this inventionare useful in hydrocarbon oils and are especially useful in lubricatingoils.

Mineral lubricating oils are susceptible to oxidation in service and instorage. Oxidation results in the formation of organic acids, aldehydes,ketones, etc. These products, especially the organic acids, arecorrosive to metal and are a principal cause of excessive wear of themetal parts coming into contact with the oil. Oxidation also results inthe formation of products which have a tendency to agglomerate to formsludge and varnish-like deposits. It is thus a common practice toincorporate into lubricating oils chemical additives which are capableof inhibiting oxidation of the oil and counteracting the corrosiveaction of the oil oxidation products. Substances useful as additives forthis purpose include the metal phosphorodithioates, particularly zincand barium phosphorodithioates. The metal phosphorodithioates are alsocapable of improving the load-carrying characteristics of the oil.Hence, the use of such additives in lubricating compositions, especiallylubricating compositions intended for use under heavy load conditionssuch as encountered in the lubrication of gears and power transmittingunits is particularly wide-spread.

While the metal phosphorodithioates are effective in improving thelubricating properties of hydrocarbon oils, they are, unfortunately,themselves susceptible to deterioration upon prolonged exposure to hightemperatures. Deterioration of metal phosphorodithioates usuallymanifests itself first in the appearance of haze or sediment in thelubricating composition. It eventually results not only in the loss ofthe desirable lubricating properties of the additive but also in theformation of objectionable decomposition products. Because of suchtendency to undergo thermal decomposition, metal phosphorodithioateshave not been considered satisfactory for use in lubricatingcompositions which must be constantly exposed to high temperatures innormal usage. Thus, it will be readily appreciated that improvement inthe thermal stability of metal phosphorodithioates will greatly enhancethe utility of such additives in lubricating compositions. In accordancewith this invention, lubricating compositions containing metalphosphorodithioates may be improved with respect to their thermalstability by the incorporation therein of a novel additive describedhereinbelow.

Accordingly it is an object of this invention to provide a process forpreparing novel compositions of matter.

It is another object of this invention to provide compositions useful asadditives in hydrocarbon oils.

It is another object of this invention to provide hydrocarbon oilcompositions having improved detergent properties.

It is another object of this invention to provide improved lubricatingoil compositions.

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It is another object of this invention to provide additives adaptedespecially for use with metal phosphorodithioates in hydrocarbon oils.

It is also an object of this invention to provide lubricatingcompositions containing metal phosphorodithioates which compositions arecharacterized by an improved resistance to thermal deterioration.

These and other objects are attained in accordance with this inventionby providing a process for preparing acylated amines which comprisesheating at a temperature above about C. an alkylene amine with fromabout 0.5 to about 1 equivalent for each equivalent of the alkyleneamine used of an acidic mixture consisting of a hydrocarbon-substitutedsuccinic acid having at least about 50 aliphatic carbon atoms in thehydrocarbon radi cal and an aliphatic mono-carboxylic acid, the ratio ofequivalents of said succinic acid to said mono-carboxylic acid in saidacidic mixture being from about 1:01 to about 1:1 and removing the Waterformed thereby.

The term alkylene amine is used herein in a generic sense to denote aclass of polyamines conforming for the most part to the structure inwhich x is an integer preferably less than about six and the alkyleneradical is preferably a lower alkylene radical such as ethylene,propylene, trimethylene, tetramethylene, or the like. Thus, it includes,for example, ethylene diamine, diethylene triamine, triethylenetetramine, tetraethylene pentamine, trimethylene diamine, propylenediamine, tetramethylene diamine, butylene diamine, N-aminoethyltrirnethylene diamine, N-dodecyl propylene diamine, di-(trimethylene)triamine, pentaethylene hexamine, etc. It includes also higher andcyclic homologues of such amines such as piperazines. The ethyleneamines are especially useful. They are discussed in some detail underthe heading Ethylene Amines in Encyclopedia of Chemical Technology Kirkand Othmer, volume 5, pages 898905, Interscience Publishers, New York(1950). Such compounds are prepared most conveniently by the reaction ofalkylene dihalide, e.g., ethylene dichloride, with ammonia or primaryamines. This reaction results in the production of somewhat complexmixtures of alkylene amines including cyclic condensation products suchas piperazine, N-aminoethyl-piperazine, etc. These mixtures find use inthe process of this invention. On the other hand, quite satisfactoryproducts may be obtained also by the use of pure alkylene amines. Anespecially useful alkylene amine for reasons of economy as well aseffectiveness of the products derived therefrom is a mixture of ethyleneamines prepared by the reaction of ethylene chloride and ammonia havinga composition which corresponds to that of tetraethylene pentamine.

The aliphatic mono-carboxylic acids contemplated for use in the processof this invention include saturated and unsaturated acids. Examples ofuseful acids are acetic acid, chloroacetic acid, dodecanoic acid,butanoic acid, palmitic acid, decanoic acid, oleic acid, stearic acid,linoleic acid, linolenic acid, naphthenic acid, chlorostearic acid,formic acid, tall oil acid, etc. Acids having 12 or more aliphaticcarbon atoms, particularly stearic acid and oleic acid, are especiallyuseful.

Aliphatic mono-carboxylic acids useful in the process of this inventionmay be iso-aliphatic acids, i.e., acids having one or more lower acyclicpendant alkyl groups. The iso-aliphatic acids result in products whichare more readily soluble in hydrocarbon oils at relatively highconcentrations and more readily miscible with other additives in theoil. Hence, they are preferred especially when the products of theprocess are to be used in lubricants containing other additives. Suchacids often contain a principal chain having from 14 to 20 saturated,aliphatic carbon atoms and at least one but no more than about fourpendant acyclic alkyl groups. The principal chain of the acid isexemplified by radicals derived from tetradecane, pentadecane,hexadecane, heptadecane', octadecam, and eicosane. The pendant group ispreferably a lower alkyl radical such as methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, tert-butyl, n-hexyl, or other radicalhaving less than about 6 carbon atoms. The pendant group may also be apolar-substituted alkyl radical such as chloromethyl, bromobutyl,methoxyethyl, or the like, but it preferably contains no more than onepolar substituent per radical. Specific examples of such acids areiso-aliphatic acids such as IO-methyl-tetradecanoic acid,ll-methyl-pentadecanoic acid, 3-ethylhexadecanoic acid,IS-methyl-heptadecanoic acid, l6-methyl-heptadecanoic acid,6-methyl-octadecanoic acid, 8-methyl-octadecanoic acid,IO-methyl-octadecanoic acid, 14-methyl-octadecanoic acid,16-methyl-octadecanoic acid, 15-ethy1-heptadecanoic acid,3-chloromethyl-nonadecanoic acid, Z-methyl-eicosanoic acid,9,IO-dimethyl-octadecanoio acid, 7,8,9,ltetramethyl-octadecanoic acid,and 2,9,l0-trirnethyl-octadecanoic acid.

An especially useful class of iso-aliphatic acids are the mixtures ofbranch-chain acids prepared by the isomerization of commercial fattyacids. A particularly useful method comprises the isomerization of anunsaturated fatty acid having from 16 to 20 carbon atoms, by heating itat a temperature above about 250 C. and at a pressure between about 200and 700 p.s.i. (pounds per square inch), distilling the crude isomerizedacid, and hydrogenating the distillate to produce a substantiallysaturated isomerized acid. The isomerization is promoted by a catalystsuch as mineral clay, diatomaceous earth, aluminum chloride, zincchloride, ferric chloride, or some other Friedel-Crafts catalyst. Theconcentration of the catalyst may be as low as 0.01%, but more oftenfrom 0.1% to 3% by Weight of the isomerization mixture. Water alsopromotes the isomerization and a small amount, from 0.1% to by weight,of water may thus be advantageously added to the isomerization mixture.

A by-product of the isomerization process is a polymerized unsaturatedfatty acid. This product can be removed as the residue by distillationor as the insoluble fraction by solvent extraction, precipitation, orfiltration of the reaction mixture. On the other hand, the desiredisomerized product can be recovered, as above, as the distillate,usually by heating the reaction mixture under vacuum. The distillate maycontain also the unreacted portion of the unsaturated fatty acid.However, upon hydrogenation, the isomerized acid and the unused starting acid yield significantly difierent products which can be separatedby solvent extraction and precipitation. Thus, the hydrogenated productof the unreacted starting acid will be considerably higher melting andless soluble in a solvent such as acetone. The hydrogenation can beeffected by any one of the well known methods such as catalytichydrogenation in the presence of Raney nickel or platinum. The productof the hydrogenation should have an iodine number less than about 10.

The mechanism of the isomerization is not known. It is known, however,that the product of the isomerization is monomeric but structurallydifferent from the starting acid in that its hydrocarbon radical nowcontains at least one branched chain.

The unsaturated fatty acids from which the iso-aliphatic acids may bederived include, in addition to oleic acid mentioned above, linoleicacid, linolenic acid, or commercial fatty acid mixtures such as tall oilacids containing a substantial proportion of unsaturated fatty acids.

The term succinic acids as used herein includes both the succinic acidsand the anhydrides of the acids. The anhydrides are preferred because oftheir greater reactivity. The hydrocarbon-substituted succinic acidsuseful in the process of this invention are those in which thehydrocarbon radical may be exemplified by an alkyl or alkenyl group andcontains at least about 50 aliphatic carbon atoms. They are commonlyderived from polyolefins such as polyethylene, polypropene, polybutene,etc. having molecular weights of 750 or higher. They may be likewisederived from substantially aliphatic hydrocarbon substances such ascopolymers of isobutene with styrene. In the latter case the copolymerswill be substantially aliphatic i.e., they will contain at least aboutby weight of the units derived from aliphatic olefinic monomers.

The hydrocarbon-substituted succinic anhydrides are readily availablefrom the reaction of maleic anhydride with a high molecular weightolefin or a chlorinated high molecular weight hydrocarbon. The reactioninvolves merely heating the two reactants at a temperature about 200 C.The product from such a reaction is an alkenyl succinic anhydride. Thealkenyl group may be hydrogenated to an alkyl group. The anhydride maybe hydrolyzed by treatment with water or steam to the correspondingacid. A particularly preferred source of the hydrocarbon-substituent inthe succinic acid is a polymer of lower mono-olefins having up to 6carbon atoms such as polybutenes. The use of polyolefins havingmolecular weights of 10005000 is preferred. Higher molecular weightpolyolefins such as those having molecular weights from about 10,000 toabout 100,000 or even higher have been found to impart also viscosityindex improving properties to the product of this invention. In manyinstances, the use of such higher molecular weight polyolefins isdesirable. Other sources of the hydrocarbon substituent includepetroleum fractions such as waxes, mineral oils, still bottoms, etc.

The size of the hydrocarbon substituent in the succinic acid moleculeappears to determine the effectiveness of the product of this process asan additive in hydrocarbon oils for the purpose of this invention.Substituted succinic acids and their derivatives have been known forsome time. It has likewise been known that these compounds are useful inlubricants, but their utility hereto fore has been predicated upon theirrust-preventing properties, corrosion-inhibiting properties, etc. Theuseful ness of compositions of this type for the purpose of thisinvention has never been realized and an important aspect of thisinvention resides in the discovery that by increasing the size of thisparticular substituent an entirely new property can be incorporated intothe composition.

The process of this invention comprises essentially the acylation of thealkylene amine with all of the acid radicals in both thehydrocarbon-substituted acid and the mono-carboxylic acid used. Theacylation is accompanied by the formation of approximately one mole ofwater for each equivalent of the acid radical used. The productresulting from the process is substantially nonacidic, i.e., it has anacid number as determined by ASTM Procedure D974-58T less than 10. Theprecise composition of the product is not known. It appears that theproduct comprises predominantly amides and imides and may contain cyclicor polyamide linkages. The relative proportions of these substances inthe product are not known. Also, a very small amount of aminecarboxylate salts, imidazolines and polyamidines may be formed but thesedo not amount to an appreciable proportion in the product.

The relative proportions of the reactants to be used in the process ofthis invention are such that for each equivalent of the alkylene amineused, there is employed from about 0.5 to about 1 equivalent of theacidic mixture of a hydrocarbon-substituted .succinic acid and amono-can boxylic acid in respective ratios of equivalents within therange from about 120.1 and about 1:1. It will be noted that theequivalent weight of the alkylene amine is based upon its nitrogencontent and that the equivalent weight of the acid reactant is basedupon the number of acid radicals in the molecule. Thus, one mole ofalkylene amine has as many equivalents as there are nitrogen atoms inthe molecule, one mole of the succinic acid or anhydride has twoequivalents and one mole of the mono-carboxylic acid has one equivalent.The above limits with respect to the relative proportions of reactantsare predicated upon the stoichiometry of the reaction involved in theprocess and also the utility of the products for the purposes of thisinvention. For example, the use of more than one equivalent of theacidic mixture for one equivalent of the alkylene amine used results inproducts having excessive acidity and corrosive tendencies. On the otherhand, the use of lesser amounts of the acidic mixture limited by aminimum of 0.5 equivalent for each equivalent of the alkylene amine usedresults in products having unreacted free amino-nitrogen atoms. Suchproducts have been found to be useful and are therefore contemplatedwithin the scope of this invention. Again based upon consideration ofutility, the preferred amount of the acidic mixture to be used in theprocess is one equivalent for each equivalent of the alkylene amine usedand the preferred ratio of equivalents of the hydrocarbon-substitutedsuccinic acid and the mono-carboxylic acid in the acidic mixture arewithin the range from 1:0.25 to 120.5.

The process of this invention may be carried out in either of two ways.It may be carried out by heating a mixture of thehydrocarbon-substituted succinic acid, the mono-carboxylic acid and thealkylene amine. Alternatively it may be carried out by first reactingthe alkylene amine with the hydrocarbon-substituted succinic acid toform an intermediate product and then reacting further the intermediateproduct with the mono-carboxylic acid. A critical aspect in carrying outthe process is that the alkylene amine should not be allowed to reactwith the mono-carboxylic acid in the absence of the succinic acidreactant. If such reaction is allowed to take place, the final product,i.e., the final product obtained by reacting further such product withthe hydrocarbon-substituted succinic acid is unsatisfactory. Thus, forexample, such final product has been found not only to possess nodetergent properties but to be capable of promoting the tendency to formharmful deposits of hydrocarbon compositions to which it has been added.The reason for the critical difference between such product and theproducts obtained by the process of this invention is not known.

The acylation reaction which characterizes the herein described processrequires a minimum temperature of about 80 C. The preferred temperatureis between 15 0 C. and 250 C. Higher temperatures may be used, providedthat such temperatures do not cause decomposition of the components ofreaction mass.

As indicated previously, the reaction involved in the process of thisinvention is accompanied by the formation of approximately one mole ofwater for each equivalent of the acid radical used. The removal of thewater formed may be effected conveniently by heating the product at atemperature above about 100 C. preferably in the neighborhood of about150 C. The removal of water may be facilitated by blowing the reactionmixture with an inert gas such as nitrogen during such heating. It maylikewise be facilitated by the use of a solvent which forms an azeotropewith water. Such solvents are exemplified by benzene, toluene, naphtha,n-hexane, xylene, etc. The use of such solvent permits the removal ofwater at a lower temperature, e.g., 80 C.

The following examples illustrate in greater detail the processes ofthis invention.

EXAMPLE 1 A mixture of 140 parts (by weight) of a mineral oil, 174 partsof a polyisobutene (molecular weight 1000)- substituted succinicanhydride having an acid number of 105 and 23 parts of stearic acid isprepared at 90 C. To this mixture there is added 17.6 parts of a mixtureof polyalkylene amines having an overall composition corresponding tothat of tetraethylene pentamine at C. throughout a period of 1.3 hours.The reaction is exothermic. The mixture is blown at 225 C. with nitrogenat a rate of 5 pounds per hour for 3 hours whereupon 47 parts of anaqueous distillate is obtained. The mixture is dried at 225 C. for 1hour, cooled to C. and filtered. The filtrate is found to have thefollowing analysis:

Percent N Acid number EXAMPLE 2 A mixture of 600 grams 1.14 equivalents)of the polyisobutene-substituted succinic anhydride of Example 1 and 161grams (0.57 equivalent) of stearic acid in 540 grams of mineral oil isprepared and heated to 80 C., whereupon 73 grams (1.7 equivalents) ofthe polyalkylene polyamine mixture of Example 1 is added to the mixtureat 80-90 C. throughout a period of 45 minutes. The

resulting mixture is heated gradually to 210 C. and then at 210225 C.for 1 hour while being purged with nitrogen. A total of 30 cc. of anaqueous distillate is collected. The residue is cooled and filtered. Thefiltrate is found to have the following analysis:

Percent N 1.83 Acid number 8 EXAMPLE 3 Percent N 1.89

Acid number 5 EXAMPLE 4 A mixture of 528 grams (1 equivalent) of thepolyisobutene-substituted succinic anhydride of Example 1, 295 grams (1equivalent) of a fatty acid derived from distillation of tall oil andhaving an acid number of 190, 200 grams of toluene and 85 grams (2equivalents) of the polyalkylene polyamine mixture of Example 1 isheated at the reflux temperature while water is removed by azeotropicdistillation. The toluene is removed by distillation and the mixtureheated at 180- 190 C. for 2 hours, then to C./20 mm. The residue isfound to have the following analyses:

PercentN 3.3 Acid number 9.8

EXAMPLE 5 A mixture of 33.2 grams (0.93 equivalent) of diethylenetriamine, 100 grams (2.77 equivalents) of triethylene tetramine, 1000grams (1.85 equivalents) of the polyisobutene substituted succinicanhydride of Example 1 and 500 grams of mineral oil is prepared at100109 C. and heated at l70 C. for 1 hour. The mixture is cooled andmixed with 266 grams (1.85 equivalents) of Z-ethyl hexanoic acid at 75-80 C. and the resulting mixture is heated at 160-165 C. for 12 hours. Atotal of 64 grams of water is removed as distillate. The residue isdiluted with 390 grams of mineral oil, heated to 160 C. and filtered.The filtrate is found to have the following analysis:

Percent N 7 EXAMPLE 6 A mixture of 100 grams (2.77 equivalents) oftriethylene tetramine, 30 grams (0.96 equivalent) of di ethylenetriamine, 1000 grams (1.85 equivalents) of the polyisobutene-substitutedsuccinic anhydride of Example .1, 266 grams (1.85 equivalents) of2-ethyl hexanoic acid and 500 grams of mineral oil is prepared at 5090C. and heated at 145 180 C. for 11 hours while nitrogen is passedthrough the mixture throughout the period. A total of 37 grams of wateris collected as distillate. The residue is diluted with 403 grams ofmineral oil, heated to 160 C. and filtered. The filtrate is found tohave the following analysis:

Percent N 2.3

EXAMPLE 7 To a mixture of 528 grams (1 equivalent) of thepolyisobutene-substituted succinic anhydride of Example 1, 30 grams (0.5equivalent) of glacial acetic acid in 402 grams of mineral oil there isadded 64 grams (1.5 equivalents) of the polyalkylene polyamine mixtureof Example 1 at 7085 C. in A hour. The mixture is purged with nitrogenat 210220 C. for 3 hours and then heated to 210 C./50 mm. The residue iscooled and filtered at 7090 C. The filtrate is found to have a nitrogencontent of 2% and an acid number of 2.

EXAMPLE 8 To a solution of 815 grams (1.5 equivalents) of thepolyisobutene-substituted succinic anhydride of Example 1 and 148 grams(0.5 equivalent) of the tall oil fatty acid of Example 4 in 750 cc. oftoluene there is added 85 grams (2 equivalents) of the polyalkylenepolyamine mixture of Example 1 throughout a period of 1 hour. Themixture is heated at reflux temperature (130 C.) for 5 hours whereupon 8cc. of water is collected in an azeotropic mixture with toluene. Theresidue is then heated to 150 C./20 mm. to remove toluene. The residueis found to have a nitrogen content of 2.85%.

EXAMPLE 9 A mixture of 792 grams (1.5 equivalents) of thepolyisobutene-substituted succinic anhydride of Example 1, 148 grams(0.5 equivalent) of the tall oil fatty acid of Example 4, 85 grams (2equivalents) of the polyalkylene polyamine mixture of Example 1 and 150cc. of toluene is heated at 180 C. 5 hours. A total of 22 grams of wateris collected as the distillate. The residue is heated to 150 C./ 20 mm.The residue is found to have a nitrogen content of 2.9%.

EXAMPLE 10 A mixture of 100 parts of tall oil fatty acids and 2 parts ofwater is heated in an autoclave at 370 C. at a pressure of 550 p.s.i.for 1.5 hours and then subjected to distillation under vacuum. Thedistillate, 96.5 parts, is hydrogenated with a Raney nickel catalystuntil its iodine number is reduced to about 7. The hydrogenated productis dissolved in a mixture of 90 parts of acetone and 10 parts of waterand the solution is chilled to precipitate as a solid the hydrogenatedproduct of the unused portion of the starting acid. The solvent in theliquid product is allowed to evaporate and the residue is a liquidisomerized acid (34 parts) having an iodine number of 10 and at leastone branched chain (shown by infrared analysis). A mixture of 200 parts(by weight) of toluene, 340 parts (9.1 equivalents) of triethylenetetramine, 112 parts (3.2 equivalents) of diethylene triamine, 1897parts (6.3 equivalents) of the iso-aliphatic acid having an acid numberof 186 and 3300 parts (6.3 equivalents) of the polyisobutene substitutedsuccinic anhydride of Example 1 is heated at 140-210 C. for 20 hourswhereupon water and toluene are removed by distillation. The residue ismixed with an equal volume of mineral oil and heated to 170 C./1 mm. andfiltered.

8 EXAMPLE 11 A mixture of 100 parts of tall oil acids, 2 parts of Water,and 2 parts of mineral clay is heated at 230 C. for 3 hours and thensubjected to distillation under vacuum. The distillate, 58 parts, has aniodine number of 103 and is hydrogenated in the presence of a Raneynickel catalyst until the iodine number is reduced to 8. The liquidisomerized acid product (obtained by the solvent extraction andprecipitation method as described in Example 1) is found to have aniodine number of 11 and at least one branched chain (shown by infraredanalysis). An oil-soluble composition is prepared by reaction of thisacid with the polyisobutene-substituted succinic anhydride and the aminemixture of Example 1, in accordance with the procedure of Example 1.

EXAMPLE 12 A mixture of 100 parts of oleic acid, 2 parts of water, and 4parts of a mineral clay is heated at 230 C. for 3 hours and thensubjected to distillation under vacuum. The distillate is hydrogenatedin the presence of a Raney nickel catalyst until the iodine number isreduced to 6. The liquid isomerized acid product (obtained by solventextraction and precipitation as described in Example 1) is found to havean iodine number of 8 and at least one branched chain (shown in infraredanalysis). An oilsoluble, nitrogen-containing composition is prepared byreaction of this acid with the polyisobutene-substituted anhydride andthe amine mixture of Example 1, in accordance with the procedure ofExample 1.

EXAMPLE 13 An iso-aliphatic acid (43 parts by weight) obtained by aprocedure substantially the same as is described in Example 10 andhaving an acid number of 176, and the isobutene substituted succinicanhydride of Example 1 (456 parts), are mixed with 186 parts of mineraloil. The mixture is added at -107 C. to 182 parts of mineral oil and 78parts of the amine of Example 1. The resulting mixture is blown withnitrogen at 205 210 C. for 8 hours whereupon volatile components aredistilled ofl. The residue is cooled and filtered at 138 C. .Thefiltrate, 904 parts (representing 97% of the theoretical yield), is thedesired product and has a nitrogen content of 2.7%.

The products of the process of this invention are for the most partliquids or semi-solids. They are soluble in hydrocarbon oils and areuseful as additives in hydrocarbon oils such as fuel oils, gasolines,metal Working oils, lubricating oils, etc. They are especially effectiveas additives to impart detergent properties to the oil, and thus toprevent the deposition of sludgeor varnishlike substances from the oil.They are also effective in improving the thermal stability ofhydrocarbon oils containing metal phosphorodithioates. The metalphosphoroditbioates which are most commonly used in hydrocarbon oilsinclude the salts of metals in group II of the Periodic Table,particularly barium and zinc, of phosphorodithioic acids having theformula wherein R and R are organic radicals such as alkyl, alkaryl,arylalkyl, and cycloalkyl radicals. Those metal phosphorodithioates inwhich the R and R radicals contain a minimum 7.5 aliphatic carbon atomsper each phosphorus atom are most readily soluble in oils and are,therefore, preferred for such use. For reasons of economy, the R and Rradicals in the phosphorodithioic acids are preferably low molecularWeight alkyl radicals and lower alkylphenyl radicals. Illustrative alkylradicals include methyl, ethyl, isopropyl, isobutyl, n-butyl, secbutyl,n-pentyl, neopentyl, S-methyl-butyl, n-heptyl,

methyl-isobutyl, 2-ethyl-hexyl, di-isobutyl, iso-octyl, decyl, etc.Illustrative cycloalkyl radicals and lower alkylphenyl radicals includecyclopentyl, cyclohexyl, methyl-cyclohexyl, butyl-phenyl, amylphenyl,diamylphenyl, octylphenyl, polyisobutyl (molecular weightl000)-substituted phenyl, etc. Other hydrocarbon radicals such astetradecyl, octadecyl, eicosyl, butylnaphthyl, hexylnaphthyl,cyclohexylphenyl, naphthenyl, etc. likewise are useful. Many substitutedhydrocarbon radicals such as chloroalkyl, dichlorophenyl andchloroalkylphenyl radicals may also be used.

The availability of the phosphorodithioic acids from which the metalsalts are prepared is well known. They are prepared for example, by thereaction of phosphorus pentasulfide with an alcohol or phenol. Thereaction involves 4 moles of the alcohol or phenol per mole ofphosphorus pentasulfide and may be carried out within the temperaturerange from about 50 C. to about 200 C. and preferably from about 80 C.to about 120 C. Thus, the preparation of di-n-hexylphosphorodithioicacid involves the reaction of phosphorus pentasulfide with 4 moles ofn-hexyl alcohol at about 100 C. for about 2 hours. Hydrogen sulfide isliberated and the residue is the defined acid. The preparation of themetal salt of this acid may be effected by reaction of the acid with ametal neutralizing agent such as zinc oxide. Simply mixing and heatingthese reactants is sufficient to cause the neutralization to take placeand the resulting product is sufficiently pure for the purpose of thisinvention.

Especially useful metal phosphorodithioates can be prepared fromphosphorodithioic acids which in turn are prepared by the reaction ofphosphorus pentasulfide with mixtures of alcohols. The use of mixturesof alcohols enables the utilization of cheaper alcohols which in themselves do not yield oil-soluble phosphorodithioate acid salts. Thus, amixture of isopropyl and hexyl alcohols can be used to produce a veryeffective oil soluble metal phosphorodithioate. For the same reasonmixtures of simple acids i.e., acids prepared from a single alcohol, canbe reacted with the metal neutralizing agent to produce less expensiveoil-soluble metal salts.

The amount of the products of this invention to be used sufiicient toimprove the thermal stability of hydrocarbon compositions containingmetal phosphorodithioate additives will vary according to the amount ofthe metal phosphorodithioate additive present therein. In mostcompositions such as those useful as lubricants for internal combustionengines, gears, power-transmitting units, the phosphorodithioateadditive should be present in amounts to impart from about 0.01% toabout 0.5% by weight of phosphorus to the compositions. It has beenfound that from about 0.05% to about 5% by weight of the products ofthis invention usually will suffice to improve the thermal stability ofsuch compositions. When used as additives to impart detergent propertiesto hydrocarbon oils, the products of this invention may be used inamounts ranging from about 0.001% to about by weight or even more.Further, for use in fuel oils, the concentration should be within therange from about 0.001% to about 0.5%, and when used in lubricatingoils, the amount may be from about 0.1% to about 10%.

The eifectiveness of the products of this invention in improving thethermal stability of lubricating compositions containing metalphosphorodithioates is shown by data obtained from a test in which a 20cc. sample of a lubricating composition placed in a inch glass test tubehaving immersed therein a strip (2 x 0.5 inch) of 10-20 steel as acatalyst to promote deterioration is maintained at 295 F. until thefirst appearance of haze or sediment. The thermal stability of thelubricating composition is measured by the time in hours required forthis appearance of haze or sediment. The results are summarized in TableI. The lubricating base oil used in this test is a SAE 90 grade minerallubricating oil. All percentages are by weight.

The eflicacy of the products of this invention as additives which impartdetergency to hydrocarbon oils is shown by the comparative data of TableH. This data was acquired from a test in which a 350 cc. sample of aMid-Continent, conventionally refined lubricating oil having a viscosityof 200 SUS/ F. containing 0.001% by Weight of iron naphthenate (as apromoter of oil degradation) and a specified amount of the detergentadditive to be tested, is placed in a boro-silicate tube. A 1%" x 5 /8"SAE 10-20 steel panel is immersed in the oil. The sample is then heatedat 300 F. for 48 hours while air is bubbled through the oil at a rate of10 liters per hour. The oxidized sample is cooled to F., mixed with 0.5%by weight of water, homogenized, allowed to stand at room temperaturefor 24 hours and then filtered through 2 layers of number 1 Whatmanfilter paper at 20 mm. mercury pressure. The precipitate is washed withnaphtha and dried. The weight of the precipitate expressed as milligramsper 100 cc. of the oil is taken as a measure of the detergent propertiesof the lubricating composition, i.e., the greater the weight of theprecipitate the less effective the detergent properties. The appearanceof the steel panel is also noted and rated on a numerical scale from 0indicating a heavy deposit to 10 indicating no deposit.

Table l Additives in Lubricant Test Result Lubricant Hours to SampleDevelopment N 0. Metal Acylated of Haze or Phosphorodithioate AlkyleneAmine Sediment 1 0.32% of phosphorus None 2. 5

as zine di(4-methyl- Z-pentyl) phosphorodithioate. 2 do 0.25% of Product11-20 of Example 1. 3 do 0.5% of Product of 3644 Example 1. 4 0.1% ofphosphorus as None 5-7 zinc salt of phosphorodithioic acid prepreparedby reaction of P S with a mixture of 60% molepercent of 4 methyl-2-pentanol and 40% mole-percent of isopropanol. 5 do 0.5% of Product of2428 Example 1. 6 l- 0.1% of phosphorus as None 6.5-7. 5

zinc di(4-Inethyl-2- pentyl) phosphorodithioate. 7 do 0.5% of Product of2448 Example 1.

Table II Test Result Lubricant amp Acylated Alkylene Amine Additive No.by weight) Sludge Panel (mg/100 Rating cc. Oil) (0-10) None. -400 1. 01.5% of Product of Example 2 7. 8 7. 0 1.2% of Product of Example 2 13.4 7. 0 1.5% of Product of Example 3 0.9 8.0 1.5% of Product of Example4." 0.8 9.0 1.5% of Product of Example 7 1. 4 8. 0 1.5% of Product ofExample 8 11.8 6 1.5% of Product of Example 9 3. 4 8. 0

' The products of this invention are also useful as pour pointdepressants in mineral oils. For instance, the pour point of a SAE 10W30 base oil is lowered from 10 F. to F. by the incorporation therein of1% by Weight of a 60% oil solution of the reaction product of thepolyisobutene-substituted succinic anhydride of Example l (6equivalents), stearic acid (1 equivalent), and the polyethylenepolyamine of Example 1 (l4 equivalents).

The following examples illustrate the lubricating compositionscontaining metal phosphorodithioates which may be improved by theaddition thereto of products of this invention (all percentages are byweight):

LUBRICANT 1 SAE 20 mineral lubricating oil containing 0.05% ofphosphorus as zinc dicyclohexylphosphorodithioate and 0.1% of theproduct of Example 1.

LUBRICANT 2 SAE 90 mineral lubricating oil containing 0.06% ofphosphorus as zinc di(isopropylphenyl)phosphorodithioate and 0.05% ofthe product of Example 2.

LUBRICANT 3 SAE 90 mineral lubricating oil containing 0.2 of phosphorusas zinc salt of an equimolar mixture of diisopropylphosphorodithioicacid and di-hexyl phosphorodithioic acid and 0.5% of the product ofExample 3.

LUBRICANT 4 SAE 10W-30 mineral lubricating oil containing 0.15% ofphosphorus as barium di-octylphosphorodithioate, 2% as sulfate ash ofbarium mahogany sulfonate and 0.4% of the product of Example 5.

LUBRICANT 5 SAE l0W-20 mineral lubricating oil containing 0.1% ofphosphorus as zinc salt of a phosphorodithioic acid prepared by thereaction of P S with an equimolarmixture of iso-octyl alcohol andcyclohexyl alcohol, 0.1% of sulfate ash of a barium salt of an acidiccomposition prepared by hydrolyzing the reaction product of apolyisobutene (having a molecular weight of 1000) with P 8 and 0.5% ofthe product of Example 7.

LUBRICANT 6 SAE 90 mineral gear lubricating oil containing 0.3% ofphosphorus as zinc dihexyl phosphorodithioate, 5% of a chlorinatedeicosane having a chlorine content of 50%, 4% of dibutyl tetrasulfide,and 0.4% of the product of Example 9.

The products of this invention are also useful in the oil-fuel mixturesfor two-cycle internal combustion engines. In this application they areefiective to reduce the engine wear and minimize the tendency of theoil-fuel mixture to cause spark plug fouling and to form harmful enginedeposits. Their effectiveness is shown by the results (Table III) of atwo-cycle engine test in which a 60-horse power, two-cycle,three-cylinder outboard motor is subjected to cycling operations, eachcycle consisting of 55 minutes of full throttle operation (5500-5600r.p.m.) and 5 minutes of idling at 600-700 r.p.m. under the followingconditions: water inlet temperature, 78-82 F.; water outlet temperature,140180 F.; and tank temperature, 95105 F. The test period of 50 or 100hours unless excessive spark plug fouling is observed. The oilfuelmixture used in the test consists of 720 (parts by volume) of a regular,leaded gasoline having an octane number of 93-94 and 18 parts of a SAE40 mineral lubricating oil containing the chemical additive. Theefiectiveness of the additive is measured in terms of the pistoncleanliness on a scale of 0 to 10 (0 being indicative of extremely heavydeposits and 10 being indicative of no deposit) and the average life ofthe spark plugs, i.e., the number of changes of spark plugs madenecessary by fouling during the test period.

The gasolines useful as the fuels for two-cycle engines may be ofregular or premium grade having an octane number from about to about110. They may contain an anti-knock agent such as tetraethyl lead ortetramethyl lead and a scavenger such as ethylene dibromide or ethylenedichloride. In lieu of the gasoline, diesel fuel likewise is useful intwo-cycle internal combustion engines. The lubricating base oils usefulin the oil-fuel mixture for two-cycle engines are usually characterizedby viscosity values from about 30 to about 200 SUS (Saybolt UniversalSeconds) at 210 F. The most commonly used oils are the minerallubricating oils having viscosity values from about 40 to about SUS at210 F. They are exemplified by mineral lubricating oils of SAE 10 to SAE50 grades.

The relative proportions of the lubricating oil to the gasoline in theoil-fuel mixture may vary within Wide ranges such as from a ratio ofabout 1:120 to a ratio of about 1:5, respectively, by volume. Thepreferred ratio is from about 1:10 to about 1:60, respectively, of thelubricating oil to the gasoline.

The oil-fuel mixtures for two-cycle engines may contain other additivessuch as metal-containing detergents, corrosion-inhibiting agents,oxidation-inhibiting agents, etc. The metal-containing detergents areexemplified by the alkaline earth metal salts of oil-soluble acids,e.g., mahogany sulfonic acid and didodecylbenzene sulfonic acid. Themetal salts include both the normal salts and the basic salts, thelatter describing the metal salts in which the metal is present in astoichiometrically greater amount than the organic acid radical.Specific examples of the metal-containing detergents are calcium salt ofmahogany sufonic acid, strontium salt of mahogany sulfonic acid, basicbarium salt of didodecylbenzene sulfonic acid obtained by carhonating amixture of a mineral oil, a sulfonic acid and barium hydroxide (5chemical equivalents per equivalent of the acid) in the presence of apromoting agent such as octylphenol (one equivalent per equivalent ofthe acid). Other metal-containing detergents include the alkaline earthmetal salts of organic phosphorus acids prepared by the treatment of anolefin polymer (such as polyisobutene having a molecular weight of about1000) with a phosphorus sulfide (such as phosphorus pentasulfide orphosphorus heptasulfide). These metal salts likewise may be normal orbasic salts.

The corrosion-inhibiting agents and the oxidation-inhibiting agents areexemplified by phenolic compounds such as 2,6-dibutyl-4-methylphenol,4,4'-methylene-bis(2- tert-butyl 6 isopropylphenol),2-methyl-6-tert-butyl-4- heptylphenol, and sulfurized heptylphenol,Arylamines and sulfurized hydrocarbons likewise are useful as inhibitmgagents. They include, for example, sulfurized dipentene (obtained by thereaction of two moles of dipentene with one mole of sulfur at C.), thereaction product of turpentine (4 moles) with phosphorus pentasulfide (113 mole), N,N'-dibutyl phenylenediamine, N-phenyl naphthylamine anddibutyl tetrasulfide.

The concentrations of the chemical additives in the oilfuel mixturesdepend to some extent upon the oils and fuels used and the types ofservice to which the oil-fuel mixtures are to be subjected. In mostapplications the nitrogen-containing composition of the invention ispresent in the oil-fuel mixture at concentrations ranging from 0.001% toabout 2%, preferably from 0.01% to 3% by weight of the mixture. Theconcentration of the other additives may each range from 0.0001% to 2%by weight of the mixture.

The following examples illustrate further the fuel-oil mixturescontaining the oil-soluble, nitrogen-containing compositions of thisinvention (the relative proportions of the fuel and the lubricating oilare expressed in parts by volume whereas the concentration of theadditives are expressed in percentages by weight of the oil-fuelmixture).

EXAMPLE A SAE 20 mineral lubricating oil parts 1 Gasoline having anoctane number of 98 ..do 20 The product of Example 1 percent 0.15

EXAMPLE B SAE 30 mineral lubricating oil parts 1 Gasoline having anoctane number of 100 do 16 The product of Example 2 percent 0.05

EXAMPLE C SAE 50 mineral lubricating oil parts 1 Gasoline having anoctane number of 85 do 30 The product of Example 3 "percent..- 0.1

EXAMPLE D SAE 40 mineral lubricating oil parts 1 Gasoline having anoctane number of 95 do 50 The product of Example 4 percent 0.054,4'-methylene-bis(2,6-ditert-butylphenol) do 1 EXAMPLE E SAE 60 minerallubricating oil parts 1 Gasoline having an octane number of 99 do 20 Theproduct of Example 1 percent 0.025 Barium salt of mahogany sulfonic aciddo 0.01

What is claimed is:

1. A process for preparing acylated amines by the reaction of analkylene amine having the structural formula in which x is an integerless than about 6 and R is a lower alkylene radical with a substitutedsuccinic compound selected from the class consisting of olefin polymersubstituted succinic acids and anhydrides having at least about 50aliphatic carbon atoms in the olefin polymer substituent and analiphatic hydrocarbon mono-carboxylic acid having up to about 22 carbonatoms, the total amounts of the succinic compound and themono-carboxylic acid used being from about 0.5 to about 1 equivalent perequivalent of the alkylene amine used and the ratio of equivalents ofthe succinic compound used to the monocarboxylic acid being from 1:0.1to about 1:1; said process comprising the steps of preparing a mixtureof the alkylene amine with the substituted succinic compound, heatingsaid mixture at a temperature from about 80 C. to about 250 C. to forman acylated intermediate, preparing a second mixture of the acylatedintermediate with the aliphatic hydrocarbon mono-carboxylic acid,heating said second mixture at a temperature from about 80 C. to about250 C. to cause further acylation, and removing the water formedthereby.

1 4 2. A process for preparing acylated amines by the reaction of analkylene amine having the structural formula equivalent per equivalentof the alkylene amine used and the ratio of equivalents of the succiniccompound used to the mono-carboxylic acid being from 1:0.1 to about 1:1;said process comprising the steps of preparing a mixture of thesubstituted succinic compound and the aliphatic hydrocarbonmono-carboxylic acid and heating said mixture with the alkylene amine ata temperature from about C to about 250 C.

3. The process of claim 2 wherein the alkylene amine is an ethyleneamine.

4. The process of claim 2 wherein the alkylene amine is a polyethylenepolyamine.

5. The process of claim 2 wherein the alkylene amine is an ethyleneamine mixture having an average of from about 2 to about 7 amino groups.

6. The process of claim 2 wherein the substituted succinic compound is apolybutene-substituted succinic anhydride wherein the polybutenesubstituent has a molecular weight above about 750.

7. The process of claim 2 wherein the aliphatic hydrocarbonmono-carboxylic acid is a fatty acid having at least about 12 aliphaticcarbon atoms.

8. The process of claim 2 wherein the aliphatic hydrocarbonmono-carboxylic acid is an iso-fatty acid having at least about 12aliphatic carbon atoms.

9. A process for preparing acylated amines which comprises the steps ofpreparing a mixture of a polyethylene polyamine having up to about 5amino groups with a polyisobutene substituted succinic anhydride whereinthe polyisobutene radical has a molecular weight of from about 750 toabout 5000, heating said mixture at a temperature from about 80 C. toabout 250 C. to form an acylated intermediate, preparing a secondmixture of said acylated intermediate with a fatty acid having fromabout 12 to about 22 carbon atoms, heating said second mixture at atemperature from about 80 C. to about 250 C. to cause further acylationand removing the water formed thereby, the total amounts of the succinicanhydride and the fatty acid being from 0.5 to about 1 equivalent perequivalent of the polyethylene polyamine and the ratio of equivalents ofthe succinic anhydride to the fatty acid being from about 1:0.25 toabout 1:1.

10. A process for preparing acylated amines which comprises the steps ofpreparing a mixture of a polyethylene polyamine having up to about 5amino groups with a polyisobutene substituted succinic anhydride whereinthe polyisobutene radical has a molecular weight of from about 750 toabout 5000, heating said mixture at a temperature from about 80 C. toabout 250 C. to form an acylated intermediate, preparing a secondmixture of said acylated intermediate with an iso-fatty acid having fromabout 12 to about 22 carbon atoms, heating said second mixture at atemperature from about 80 C. to about 250 C. to cause further acylationand removing the water formed thereby, the total amounts of the succinicanhydride and the iso-fatty acid being from 0.5 to about 1 equivalentper equivalent of the polyethylene polyamine and the ratio ofequivalents of the succinic anhydride to the iso-fatty acid being fromabout 1:0.25 to about 1:1.

11. The process of claim 10 wherein the iso-fatty acid is obtained bythe isomerization of an unsaturated fatty acid having from about 16 to'20 carbon atoms.

12. The product of the process of claim 2.

13. The product of the process of claim 11.

14. A hydrocarbon oil composition comprising a major proportion of ahydrocarbon oil and a minor amount, sufficient to improve the detergentproperty of said composition, of the product of claim 11.

15. A hydrocarbon oil composition comprising a major proportion of ahydrocarbon oil and a minor amount, sufiicient to improve the detergentproperty of said composition, of the product of claim 12.

16. A lubricating composition comprising a major proportion of a minerallubricating oil, from about 0.01% to about 0.5% of phosphorus as a GroupII metal phosphorodithioate and a small amount, sufiicient to reduce thetendency of said composition to develop haze or sediment at elevatedtemperatures due to the presence therein of said metalphosphorodithioate, of the product of claim 12.

17. The lubricating composition of claim 16 characterized further inthat the Group H metal phosphorodithioate is a zinc phosphorodithioate.

18. The lubricating composition of claim 16 characterized further inthat the Group II metal phosphorodithioate is a zinc salt of aphosphorodithioic acid having the formula wherein R and R each containup to about 10 aliphatic carbon atoms and are selected from the groupconsisting of alkyl, alkaryl, arylalkyl, and cycloalkyl radicals.

19. An oil-fuel mixture suitable for use in two-cycle engines comprisingfrom about 5 to about parts by weight of gasoline, one part of a minerallubricating oil, and a small amount, sufiicient to improve the detergentproperty of said mixture, of the product of the process of claim 2.

20. An oil-fuel mixture suitable for use in two-cycle engines comprisingfrom about 5 to about 120 parts by weight of gasoline, one part of amineral lubricating oil, and a small amount, sufiicient to improve thedetergent property of said mixture, of the product of the process ofclaim 11.

References Cited by the Examiner UNITED STATES PATENTS 2,568,876 9/61White et al. 252--51.5 3,018,247 1/ 6'2 Anderson et a1. 260--32.73,083,162 3/63 Lawrence 44-58 X DANIEL E. WYMAN, Primary Examiner.

2. A PROCESS FOR PREPARING ACYLATED AMINES BY THE REACTION OF ANALKYLENE AMINE HAVING THE STRUCTURAL FORMULA
 12. THE PRODUCT OF THEPROCESS OF CLAIM
 2. 16. A LUBRICATING COMPOSITION COMPRISING A MAJORPROPORTION OF A MINERAL LUBRICATING OIL, FROM ABOUT 0.01% TO ABOUT 0.5%OF PHOSPHORUS AS A GROUP II METAL PHOSPHORODITHIOATE AND A SMALL AMOUNT,SUFFICIENT TO REDUCE THE TENDENCY OF SAID COMPOSITION TO DEVELOPE HAZEOR SEDIMENT AT ELEVATED TEMPERATURES DUE TO THE PRESENCE THEREIN OF SAIDMETAL PHOSPHORODITHIOATE, OF THE PRODUCT OF CLAIM 12.